Nogales inhabits La Frontera, the Arizona-Mexico border country that exists as much as a state of mind as a place. Here among the saguaro under the Sonoran desert sun came conquerors under the flags of Spain, Mexico, the United States, and the Confederate States. From the arrival of Fray Marcos de Niza in the Ambos Nogales territory in 1539 when Nogales was part of New Spain, through the marches of Conquistadores along Spain's El Camino Real or Royal...